The present invention relates to articles and methods for disposing a coating material onto an end of an optical fiber to be terminated.
Optical fiber is widely being deployed for information transfer applications and in a variety of sensor applications. A common requirement in the optical fiber industry is to provide efficient and convenient methods of connecting an optical fiber to either a light source, a light detector, another optical fiber, an optical fiber coupler, etc. A common method previously proposed is to simply leave an air gap between an end of the optical fiber being terminated and its mating optical element, and this method is disadvantageous since light is required to pass from the optical fiber core, into air and then into a mating optical element (e.g. another fiber core). A difference in the indices of refraction between these adjacent materials (core, air, core) causes Fresnel reflections to be created at medium interfaces, and these reflections generate noise as well as excessive optical losses.
Another method for terminating an optical fiber requires that the fiber be disposed in physical contact with its optical element, this method being disadvantageous since the fiber end must be carefully polished to achieve acceptable throughput losses as well as to eliminate reflections. Also, the fiber end can subsequently be damaged if subjected to vibrations or during numerous mating cycles.
Oils and greases have also been proposed to be disposed in contact with an optical fiber termination so as to create a uniform index of refraction medium for the light to travel through across an optical fiber connection, however, all such methods are disadvantageous since convenient methods of applying the grease or oil have yet to be proposed.
Finally, it has also been proposed to dispose elastic materials on an end of an optical fiber contact for creating an index matching medium through which the light can pass. Specifically, U.S. Pat. No. 4,512,630 discloses a method whereby an applicator tip is disposed in a liquid and then retracted so as to hold a drop of the liquid which is then applied to an end of an optical fiber contact. The liquid is then cured on the contact end. Again, this method is disadvantageous since it is quite craft sensitive to implement, especially by unskilled workers in the field, and it also tends to be messy. In addition, it is also difficult to cure the liquid subsequent to application.
Another previously disclosed method for disposing an index matching solid substance onto an end of an optical fiber is disclosed in U.S. Pat. No. 4,436,366, this patent teaching disposing an appropriate index matching layer coating on a substrate film, then drying the coating, and then covering the coating with a protective layer. In use, the protective layer is stripped from the coating and an optical fiber contact is disposed in contact with the coating while simultaneously cross-linking the coating so as to allow it to adhere to the optical fiber contact end. Again, the disadvantage with this technique is that it is not easily implemented by relatively unskilled workers, and hence it is not convenient or economical to use in practice.
The methods of both of these patents are further disadvantageous since the fiber coatings produced are permanently applied to the fibers which allows the coatings to become contaminated or physically damaged, in which case new fiber terminations need to be prepared.